對class撰寫event

2008-05-27

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對class撰寫event

有時我們在處理class時..要撰寫物件的event..來讓其他的物件訂閱..
寫下簡單的範例.. 以後需要時自己也不會忘掉..

使用內建的delegate(EventHandler)去做

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication4
{
   public partial class Form1 : Form
   {
       public Form1()
       {
           InitializeComponent();
       }

       //建立測試按鈕事件
       private void button1_Click(object sender, EventArgs e)
       {
           ukhs obj = new ukhs();
          
           //加入訂閱事件
           obj.myEvent += new EventHandler(obj_myEvent);

           //測試
           obj.goFire();
       }

       void obj_myEvent(object sender, EventArgs e)
       {
           if (e is myEvenArg)
           {
               MessageBox.Show((e as myEvenArg).msg);
           }
       }
   }
}

//自行寫的class
class ukhs
{
   //使用內建的delegate,他需要傳遞(object sender,eventArgs e)
   public event EventHandler myEvent;
   public void goFire()
   {
       if (myEvent != null)
       {
           myEvent(this, new myEvenArg("發射飛彈!!"));
       }
   }
}

//繼承EventArgs
class myEvenArg : EventArgs
{
   public string msg { get; private set; }
   public myEvenArg(string msg)
   {
       this.msg = msg;
   }
}

也可以自行定義delegate去做

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication4
{
   public partial class Form1 : Form
   {
       public Form1()
       {
           InitializeComponent();
       }

       //建立測試按鈕事件
       private void button1_Click(object sender, EventArgs e)
       {
           ukhs obj = new ukhs();

           //加入訂閱事件
           obj.newEvent += new ukhs.myEvent(obj_newEvent);

           //測試
           obj.goFire();
       }

       string obj_newEvent(string msg)
       {
           MessageBox.Show(msg);
           return "我已經完成任務了";
       }
   }
}

//自行寫的class
class ukhs
{
   //宣到一個delegate
   public delegate string myEvent(string msg);
   public event myEvent newEvent;
   public void goFire()
   {
       //判斷是否有人訂閱
       if (newEvent != null)
       {
           //執行delegate
           string getMsg = newEvent("發射飛彈!!");
           MessageBox.Show(getMsg);
       }
   }
}

有問題在一起討論ㄅ..

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